MadBull ACE M4 stock tube installation instruction

MadBull have new M4 stock tube specially designed to store your battery:

You don’t need bulky battery box for your M4 AEG anymore. Using special design M4 stock tube to store your battery and make your AEG look like real thing!

[youtube http://www.youtube.com/watch?v=S_56s1E9eoM&hl=en]

(MadBull)